Two safety shutdown valves to protect 30% of UK energy supply

Imagine 30% of a country’s energy supply relying on two safety shutdown valves to flow natural gas and liquid condensate safely from offshore oil and gas production platforms to an onshore processing facility. It’s critical that the valve actuators reliably perform their function to close the valves when a shutdown command is issued by the safety instrumented system.

Two valve actuators Emerson has been assembling for Shell UK, in Great Britain, are far too tall and heavy to be worked on indoors. Standing 5.5 m high with a weight of 5440 kg, the actuators look like little more than long, thin tubes of steel than high-precision instruments.

Spring being mounted into the safety shutdown valve’s actuator at Emerson’s Valve Automation manufacturing facility.

Coos explained that this project included both schedule and technical challenges. From a technical standpoint, the actuation pressure required for the 76 cm gate valves would require a “never been done before” custom design. Because this valve actuator would be part of a Zone 1, IIB T3 safety instrumented function, the actuator design would require safety certification per the IEC 61508 international safety standard.

The schedule challenge was that the gas plant has a scheduled turnaround with a small time window where the shutdown valves can be installed during the production stoppage. All of the necessary equipment and cranes will be present, so any schedule slippage would be costly. The total time frame from order to shipment to site was 18 months.

Springs to meet the application requirements for the safety shutdown valves’ actuators.

The actuators were designed, engineered, built and assembled in the Emerson Process Management Valve Automation facility in Mansfield, Ohio. The design is based on the Bettis GVO Series of linear valve operators scaled up to generate the required force to hold the safety shutdown valves open under start-up and operating conditions. The actuators are a fail-close design held open by hydraulic-spring return design operating at 1900-3000 psig (131-207 bar) operating pressure. The actuator design complies with the European Commission’s Pressure Equipment Directive (PED) 97/23/EC and ATEX.